Clinical analyzers currently in use in hospitals often do not have direct or positive sample identification associated with the container of the patient's sample. That is, an operator often is required to enter patient's data into the analyzer concerning a particular container's sample. Such an approach runs some risks, in that errors can be made in either the data entry, or the placement of the container in the predicted location of the analyzer.
To overcome this problem an improved analyzer has been provided that has positive sample identification (hereinafter, PSID). As used herein, PSID refers to the automated sampling of liquids from a container bearing machine readable patient identification, thus eliminating sources of identification error. In such an analyzer, a special container is used that has a bar code label that contains the complete identity of the patient. The bar code is read by a laser prior to the sample being aspirated into the analyzer. An example of such an approach is shown in patent application WO 83/00393.
One problem with the PSID technique is that only one or at most two specially sized containers can be used--those that fit this particular analyzer. That is, the PSID analyzer will accommodate a "conventional" tubular container, and a microcontainer that is a cup that is quite different from the "normal" tubes. The two types are distinguished based on the label that is present. However, patient samples come in tubular containers having a variety of sizes. For example, there are "standard" test tube containers that are the 16 mm sizes, some that are 13 mm in diameter, some that are 10 mm, and some that are even smaller for pediatric samples. Yet, the standard tray opening in many analyzers' trays is about 16 mm. Thus, for such analyzers, a single container having a width of about 16 mm would have to be used, and all the samples arriving in the other containers would have to be transferred somehow as such other containers would be "non-standard". Pour-off is often objectionable, since it can affect such analytes as CO.sub.2, and has the potential of contamination.
Thus there has been a need, prior to this invention, to provide a PSID analyzer that will allow the direct use in that analyzer, of a variety of sizes of tubular sample containers, as supplied. Such an improved analyzer would not require the intermediate, time-consuming, and error-prone step of transfer to a special container that is the only tubular container (as opposed to a microsample container) that fits the PSID analyzer.